The present invention is directed to a hole machine, more specifically to a sewing machine for forming buttonholes or the like with lock stitches and chain stitches.
In general, a hole sewing machine is comprised of a sewing machine head, a support stand upon which the head is mounted, an electric motor for driving the head and transmission means between the motor and the head. The various mechanisms for forming the stitches are associated with the sewing machine head and include a needle bar mechanism, a feed mechanism, a looper-spreader mechanism, a cloth clamping mechanism, a cloth cutting mechanism, a sector mechanism, a looper stand mechanism, and a clutch mechanism. The feed mechanism includes cam means for controlling the movement of the needle along a button-hole shaped path and for operating the button hole cutting means.
In the operation of such a conventional buttonhole sewing machine, the sewing machine is started and upon operation of the suitable clutch mechanism the feed mechanism is energized to perform a sewing operation along the configuration of an eyelet hole which is determined by the cam means. In order to prevent irregular stitching during the sewing of the eyelet hole, the needle bar and looper stand are turned in synchronism with the stitches by the action of the cam means. When the desired number of stitches have been completed, the cloth cutting means is operated to complete a single cycle of operation and the sewing machine is automatically stopped. Depending upon the specifications of the sewing operation, the cloth cutting means may be operated prior to the sewing operation.
In the conventional buttonhole sewing machine the shape of the buttonhole is uniformly determined by the configuration of the sewing machine head and the associated cam means. Thus, while it is often desired to produce buttonholes in various patterns, the conventional buttonhole sewing machine cannot produce the various patterns. More specifically, in order to change the buttonhole sewing pattern, it is necessary to change a large number of components in the sewing machine, including the cam means for the feed mechanism. The adjustment of the length of the line portion of the buttonhole and pitch of the buttonhole sewing stitches requires specialized tools and a considerable amount of delicate adjustment work. In addition, it is impossible to separately adjust the pitch of the stitches for the straight part of the buttonhole and the round part of the buttonhole.